This section of the road follows the famous Firehole River and will lead you to the Upper, Middle and Lower Geyser Basins. Near Madison Jct is a turn off to beautiful firehole canyon and firehole falls. The Fountain Paint Pots are in the Lower Geyser Basin. Here mud boils and bubbles and sometimes spurts into the air. The mud is composed of clay and silica which was formed by chemical decomposition of rock minerals. Past the Paint Pots is a side road that leads to one of the best geysers in Yellowstone – Great Fountain Geyser. It erupts to heights of 100 to 150 feet with rare bursts reaching heights of 200 feet. Midway Geyser Basin is dominated by two gigantic features, Excelsior Geyser and Grand Prismatic Spring. Excelsior Geyser spills into the Firehole River at a rate of over 5 million gallons a day. The upper geyser basin contains two thirds of all the geysers in Yellowstone. It is highlighted by the most famous geyser in the world – Old Faithful.